Loads critical

CLAG, Critical Loads of Acidity in the United Kingdom, Summary Report of the Critical Loads... 

For critical loads and belt drives particularly, the user is advised to seek the opinion of the motor manufacturer to determine the mechanical suitability of the motor selected, its shaft and the DE bearing for the load to be transmitted, according to the drive system being adopted. The following are some important parameters that may help to determine... 

In a fixed construction, all the feeders in the switchboard, feeding the various load points, are securely mounted in the assembly and rigidly connected to the main bus. In the event of a fault in one feeder on the bus side, a shutdown of the entire switchboard may be required. A process industry or critical loads can ill afford such an arrangement. However, since this is the most cost-effective switchboard, it is also the most common type and is used extensively. It also suits all applications, except a process industry or critical loads, which may not be able to afford a total shutdown or prolonged downtime in the event of a fault. In such cases a draw-out type switchboard will prove to be a better choice as discussed below. A fixed-type construction may further be classified as follows. 

As noted from general experience, except for specific large inductive loads such as of furnace or rectifiers, the fundamental content of the load current is high compared to the individual harmonic contents. In all such cases, it is not necessary to provide a filter-circuit for each harmonic unless the current is required to be as close to a sinusoidal waveform as possible, to cater to certain critical loads or instruments and devices or protective schemes operating in the system, where a small amount of harmonics may lead to malfunctioning of such loads and devices. Otherwise only the p.f. needs be improved to the desired level. Also to eliminate a parallel resonance with the... 

Critical Load the concentration of air pollution or total deposition of pollutants above which specific deleterious effects may occur. 

Target Load the acceptable concentration or dose of an air pollutant that provides a reasonable margin of safety below the critical load. The target load should be achievable under existing conditions. 

The ecoscarcity method was developed by Ahbe et al." It is essentially based on an Ecofactor which is calculated for each emission equal to (F/Ff,) 1/Fj, X, where F is the emission in the area, F is the emission target or the critical load in the area (country), and X is a constant used for practical purposes to obtain easy-to-handle magnitudes of the figures. 

Welding. Where welding is involved in the critical load path of main load carrying components, recognized standards shall be used to qualify welders and procedures. 

Critical loads may be experienced for example, severe loads, impact loads such as jarring, pulling on stuck pipe, and/or operating at low temperatures. If in the judgment of the supervisor a critical load has occurred, or may occur, an on-the-job shutdown inspection equivalent to the periodic field inspection should be conducted before and after the occurrence of such loading. If critical... 

The periodic or critical load inspection in the field should be conducted by the crew with the inspector. For the periodic or critical load inspection, all foreign matter should be removed from surfaces inspected. Total field disassembly is generally not practical, and is not recommended, except as may be indicated in the detailed procedure for each tool. 

Standby supply systems within an electrical installation provide supplies to critical loads on loss of normal power supplies. In an installation one or more of the following types of standby supply systems are likely to be found ... 

We have discussed the value of struts or columns in structural mechanics and described their linear elastic properties. They have another characteristic that is not quite so obvious. When columns are subject to a compressive load, they are subject to buckling. A column will compress under load until a critical load is reached. Beyond this load the column becomes unstable and lateral deformations can grow without bound. For thin columns, Euler showed that the critical force that causes a column to buckle is given by... 

An accurate determination of critical load Wcr is sometimes difficult. Several techniques, such as (1) microscopic observation (optical or SEM) during the test, (2) chemical analysis of the bottom of the scratch channel (with electron microprobes), and (3) acoustic emission, have been used to obtain the critical load. 

Fig. 33—Typical scratch curve of Sample 4, Fn is the normal load. Ft is the measured tangential force, Pd is the penetration depth, Rd is the residual depth. The critical load is 86.63 mN.

A nano scratch tester (CSEM) was employed to carry out the scratch test. A Rockwell diamond tip with a radius of 2 fim was used to draw at a constant speed 3 mm/min across the coating/substrate system under progressive loading of 130 mN maximum at a fixed rate 130 mN/min. The total length of the scratch scar is 3 mm. The critical load (L ) here is defined as the smallest load at which a recognizable failure occurs. The failure can be observed both by the built-in sensors and by the optical microscope. 

Figure 33 shows a typical scratch test curve of Sample 4. Both the penetration depth and the residual depth as well as the tangential force can be obtained from this curve. The critical load can be found from the transition stages plotted in the three curves. The critical load (L ) of Sample 4 is 86.63 mN. 

Figure 34 shows the critical load of all the samples. For the monolayer samples, Sample 1 has a higher critical load than Sample 2. The multilayers Samples 4, 5, and 6 have higher critical loads than monolayer Samples 1 and 2. Samples 5 and 6 have excellent scratch resistant properties. Only extremely small cracks are found in the scratch tracks of Samples 5 and 6. Therefore, there is no sudden change found in the force and penetration depth curves. Sample 7 has the lowest critical load, similar to the monolayer Sample 2. 

Hard layer and soft layer combined together can reduce the intrinsic stress of the whole coating [17,18,22-27]. Samples 4, 5, and 6 have higher critical load than that of monolayer A and B. For Samples 5 and 6, no obvious crack occurs during the scratch test. Sample 5 has the highest hardness and reduced elastic modulus among the multilayer samples, and the interfaces in Sample 5 also contribute to scratch resistance. So it has the best micromechanical properties here. 

In addition to the properties noted above, the formulation parameter in iPP-E-plastomer blends have a profound influence on the dynamic loading (e.g., vibration) performance. The load limits of the blend for applications in which dynamic stresses are predominant were studied by using the hysteresis measurement method. However, their technical application requires knowledge of critical load values. 

The double torsion test specimen has many advantages over other fracture toughness specimen geometries. Since it is a linear compliance test piece, the crack length is not required in the calculation. The crack propagates at constant velocity which is determined by the crosshead displacement rate. Several readings of the critical load required for crack propagation can be made on each specimen. 

Hultberg H, Iverfeldt A, Lee Y-H. 1994. Methyhnercury input/output and accumulation in forested catchments and critical loads for lakes in Southwestern Sweden. In Watras C J, Huckabee. JW, editors. Mercury pollution, integration and synthesis. Boca Raton (FL) Lewis Publishers, CRC Press, Inc. 

Johansson K, Aastrup M, Andersson A, BringmarkL, Iverfeldt A. 1991. Mercury in Swedish forest soils and waters — assessment of critical load. Water Air Soil Pollut 56 267-281. 

The critical load to cause buckling in a ring under a uniform radial load Fc is given by the following expression... 

Herrera, Vargas, et al. (2) report experimental measurements of the behavior of energetic materials burning in a compartment. The results indicate that as the critical loading density, Mc (kg/m3) Increases, the mass burning rate inside the compartment reaches a steady state condition and unburned material is carried out in the plume. Burning of the unburned material then takes place outside the compartment, thereby contributing to the destructive potential of the fire in adjacent spaces. 

Meanwhile, a quantitative approach to assessing pollution effects on ecosystems has already been developed. A Critical Load and Level (CLL) concept has been used for defining emission reduction strategies under the UNECE Convention on... 

Long-range Transboundary Air Pollution (LRTAP). Over time, the critical load approach has been defined not only at international but also at regional and local levels (Posch et al., 1993, 1997, 1999, 2001, 2003 Bashkin, 1997, 2002). 

The term critical load refers only to the deposition of pollutants. Threshold gaseous concentration exposures are termed critical levels and are defined as "concentrations in the atmosphere above which direct adverse effects on receptors such as plants, ecosystems or materials, may occur according to present knowledge". 

Correspondingly, transboundary, regional or local assessments of critical loads are of concern for optimizing abatement strategy for emission of polutants and then-transport (Figure 1). 

Figure 1. Illustration of critical load and target load concepts.

The critical load concept is intended to achieve the maximum economic benefit from the reduction of pollutant emissions since it takes into account the estimates of differing sensitivity of various ecosystems to acid deposition. Thus, this concept is considered to be an alternative to the more expensive BAT (Best Available Technologies) concept (Posch et al., 1996). Critical load calculations and mapping allow the creation of ecological-economic optimization models with a corresponding assessment of minimum financial investments for achieving maximum environmental protection. 

Critical loads and levels are measurable quantitative estimates showing the degree of tolerable exposure of receptors to one or more pollutants. According to present knowledge, when this exposure remains below the critical load and level thresholds, significant harmful effects on specified receptors do not occur (Gregor, 2003). They serve as reference points against which pollution levels can be compared and potential risks to environmental components can be estimated. 

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